#include <iostream>
#include<iomanip>
#include <math.h>
using namespace std;
int main()
{
	double x, y;
	char c;
	cout << "请输入算术表达式，例如1+1" << endl;
	cin>> x>> c >> y;
	switch (c)
    {
	case '+': cout << "结果的值为：" << setprecision(2)<<x + y; 
    break;
	case '-': cout << "结果的值为：" << setprecision(2) << x - y;
     break;
	case '*': cout << "结果的值为" << setprecision(2) << x * y; 
    break;
	case '/': cout << "结果的值为:" << setprecision(2) << x / y; 
    break;
	default:cout << "你输入的表达式有错误" << endl;
	}
	return 0;
}
                                                       